Thesis (Ph.D.) - Cairo University - Faculty of Science - Department of Organic Chemistry

Six homologous series of 4-(4ʹalkoxy phenylazo) phenyl 4ʺ- substituted benzoates (Ina-f ) were prepared in which the alkoxy group n varies between 6, 8, 10 and 12 carbons, while, within the six homologous series, the terminal substituent, X, alternatively changed from CH₃O, CH₃, H, Br, NO₂ and CN. A comparative study was made between the investigated compounds and their isomers, namely, 4- (4ʹ- substituted phenylazo) phenyl- 4ʺalkoxybenzoates in which the two terminal groups are exchanged. The effect of lateral methyl substitution and its orientation on the mesophase behavior of Ina-f, were also investigated on two newly prepared homologous series of 4- alkoxyphenylazo 4ʹ- (2- (and 3-) methyl-) 4"-substituted benzoates (IIna-f and IIIna-f, six series each). All compounds prepared were characterized by infrared, mass, elemental analyses and H1-MNR spectroscopy and their transition temperatures determined by differential scanning calorimetry (DSC) and phases identified via polarized light microscopy (PLM). The results were discussed in terms of steric and polarizability effects. The mesophase stability ({u221A}TC) was correlated with the polarizability anisotropy of bonds to the terminal substituent X. Comparative studies were made between the two groups of compounds (IIna-f and IIIna-f) with each other and with their laterally neat analogues Ina-f

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